1. Field of the Invention
The invention relates to the field of grinders for reducing discarded tires into smaller pieces for disposal or recycling.
2. Description of the Related Art
The disposal of worn tires is complicated by the material characteristics that are designed into them. Thus, the tendencies of modern tires toward structural integrity and weather resistance that make them serviceable for long periods of time also make their disposal more difficult. There are problems with simply placing whole tire carcasses in landfills. The voids in the carcasses give them a tendency to float to the surface over time and can cause an undesirable softness or sponginess and, thus, instability to the overall landfill. Simply accumulating tires in the open often results in water collecting in the carcasses, which promotes the breeding of mosquitos and other pests. Additionally, while tires are not highly flammable, fires occurring in large collections of tires are highly polluting, as well as difficult and dangerous to extinguish.
In order to facilitate the disposal of tires, machines have been developed to reduce tire carcasses to smaller pieces ranging in size from several inches in extent down to small pellet sizes. The larger sized xe2x80x9cchunksxe2x80x9d are suitable for further processing, such as reduction to a smaller size or, alternatively, for more convenient disposal in a land fill. The smaller pellet size particles are suitable for disposal in land fills, but also for such uses as a component of road paving materials or as a component of a fuel, as for steam generation.
Conventional machines for chopping or comminuting tire carcasses include hammer mills having rotating blades or teeth which shear the carcasses into pieces in cooperation with additional sets of counter-rotating teeth or shear bars with stationary sets of teeth. One problem with conventional tire chopping machinery is that the moving blades tend to pull the entire carcass through the sets of teeth before it can be fully reduced. This can cause a xe2x80x9cjamxe2x80x9d in the machine, requiring interruption of carcass processing and, possibly, requiring partial disassembly of the machine to clear. In some cases, damage to the machinery can occur, such as by deforming a mandrel on which the rotating tooth structures are mounted, the shear bar, or both. In any case, the oversized pieces must be retrieved and reprocessed. Often, such machinery incorporates size classifiers to separate larger pieces of tires to be reprocessed from those which can be passed on, as by a conveyor, to the next process or to a place of collection.
The present invention provides an improved tire chopping apparatus for comminuting or reducing tire carcasses to smaller fragments. The apparatus includes a support framework on which a rotor assembly is positioned, along with a stationary shear bar. The rotor assembly is formed by a central mandrel onto which are mounted a plurality of axially spaced chopper xe2x80x9cdiscsxe2x80x9d. The chopper discs are somewhat pinwheel shaped and provide a structure on which a plurality of replaceable rotor teeth are mounted. The shear bar includes a plurality of laterally spaced shear teeth which are also replaceable.
The rotor teeth, or rotor shear tools, are positioned in an outwardly or radially extending and circumferentially spaced orientation. The chopper discs are oriented in such a manner that the teeth thereon are angularly staggered from one disc to the next in a multiple xe2x80x9cchevronxe2x80x9d or V-shaped pattern of teeth in adjacent discs. In general, the staggering of the teeth limits the number of teeth xe2x80x9cbitingxe2x80x9d into a carcass at the same time to reduce the torque requirements for a rotor motor to drive the rotor assembly and to avoid bogging down such a motor. The chevron pattern of the rotor teeth is oriented in such a direction relative to rotation that carcasses are urged laterally in relation to the rotor assembly to avoid jamming of carcasses at single section of the rotor assembly. To some extent, the lateral carcass movement caused by the chevron rotor teeth pattern tends to xe2x80x9cchurnxe2x80x9d a group of tires within the hopper to thereby prevent bunching up or jamming of the apparatus by too many carcasses being fed at one time.
Additional jamming prevention is provided by a plurality of guards which are spaced along the rotor assembly and positioned respectively between the chopper discs. The guards are oriented in vertical planes and extend between the rotor assembly and the shear bar to form a xe2x80x9cclassifierxe2x80x9d or grate to limit the size of carcass fragments which can pass through a chopper or shear zone at which the rotor and shear teeth engage the carcasses. Carcass fragments too large to pass between the guards, or be driven therebetween by the rotor teeth, are positioned to be engaged and reduced by the rotor teeth in cooperation with the shear teeth.
In a first embodiment of the present invention, the guards take the form of bridge plates, which are generally C-shaped with radial extensions at the ends. The bridge plates are retained at one end by engagement or hooking under frame structure of the tire hopper and at the shear zone by the shear teeth and are, thus, removable and replaceable if worn, damaged, or dislodged. As tire carcasses are urged toward the shear teeth by contact with the moving rotary teeth, engagement of the carcasses with the bridge plates prevents them from being drawn between the rotor and shear bar. Only after the carcasses are reduced to much smaller size can they be drawn through.
In a modified embodiment of the tire chopping apparatus, the guards are in the form of upstanding guard plates which extend upwardly from the shear bar proximate each of the stationary shear teeth and outwardly toward the rotor mandrel. The guard plates are cantilevered from the shear bar so that a gap remains between the distal end of the guard plate and the rotor mandrel. The gap allows hard to grind fibrous materials, such as the steel belting from steel belted radial tires, to pass through the machine, while still preventing large pieces of tire carcass from being drawn through. The upper edge surface of each guard plate slopes downwardly toward the gap so that belt material is more likely to fall through the gap instead of building up on the guard plate. The upper edge surface may further be provided with a plurality of teeth arrayed in a ratchet or stair-step pattern to help prevent the tire carcasses from being pushed away from the shear zone by the action of the rotor.
The shear bar is mounted on its supporting framework in such a manner that a shear gap between the shear teeth and the rotor teeth can be adjusted. Adjustment of the shear gap is desirable to selectively control the shear relationship between the moving and stationary teeth. If the shear gap is too small, excessive wear, or breakage, of the teeth can occur. Conversely, too large a shear gap reduces the effectiveness of the teeth in converting the carcasses into smaller fragments and may result in jamming of the shear zone for that reason. Additionally, periodic adjustment of the shear gap is required to compensate for wear of the rotor and shear teeth. In the present chopper apparatus, the shear bar is slidably mounted on the support framework and is engaged by a mechanism such as bolts which can be driven inwardly or outwardly to adjust the position of the shear teeth relative to the rotor teeth. Once the desired position has been achieved, the bolts can be secured in position, as with lock nuts.
Although the tire chopping apparatus could be installed and operated in a stationary configuration, a preferred embodiment of the present invention is mounted on a chassis of a movable trailer or on a self-propelled vehicle. This allows more flexible and efficient use of the present invention, since it can be transported to a quantity of tire carcasses to be processed, rather than the carcasses being transported to and then from the apparatus. The apparatus support frame is mounted on the vehicle chassis and has the rotor assembly journaled thereon. The apparatus frame also supports the shear bar, the feed hopper, and the feed bumper. A rotary hydraulic motor is engaged between the support frame and the rotor assembly. The feed bumper includes one or more linear hydraulic motors or cylinders which are controlled to reciprocate the bumper toward and away from the rotor.
The chassis also preferably has a conveyor, such as a belt conveyor, positioned below the shear zone and conveys the tire carcass fragments to a storage location or container. The apparatus may also include equipment to load tire carcasses into the feed hopper, such as a grapple mounted on a boom. Although the chopping apparatus is described principally in terms of processing tire carcasses, it could also be used for other purposes, such as for comminuting refuse building materials from demolitions and rehabilitation projects, and other materials. For such other applications, some variations in dimensions, spacing of the guards, tolerances, and the like may be required, in comparison to an apparatus suitable for chopping tire carcasses. However, such variations are believed to be within the scope of the present invention.